1. Field of the Invention
The present invention relates to a catalyst for producing acrylonitrile by vapor phase ammoxidation of propylene by molecular oxygen and ammonia, and to a process for producing acrylonitrile using the catalyst.
2. Description of Related Art
Numerous proposals have been made regarding catalysts for producing acrylonitrile by vapor phase ammoxidation of propylene by molecular oxygen and ammonia. For example, catalysts have been disclosed having as main components thereof molybdenum, bismuth and iron, and which are further compounded with various metal components (Patent Documents 1 to 11).
In addition, methods for regenerating a catalyst by adding a molybdenum-containing substance to an inactivated molybdenum-containing catalyst, and methods for maintaining long-term performance of a catalyst by adding a molybdenum-containing substance to a molybdenum-containing catalyst, have been proposed (Patent Documents 12 to 16).
A method was found for greatly improving the selectivity of acrylonitrile by using one or more elements selected from the group consisting of potassium, rubidium and cesium as trace essential alkaline metal elements contained in catalysts used in the reactions described above, and controlling the amounts thereof within a proper range, while also inhibiting reductions in acrylonitrile yield over time by replenishing with a catalyst having a high content of alkaline metal elements since the alkaline metal elements are lost in the reaction (Patent Document 17).
In addition, in the case of adding sodium to a catalyst, the sodium was found to not only strengthen attrition resistance, but also enhance both the degree of activity and selectivity when used with a specific element (germanium) (Patent Document 18).
[Patent Document 1] U.S. Pat. No. 5,212,137
[Patent Document 2] U.S. Pat. No. 5,688,739
[Patent Document 3] U.S. Pat. No. 5,834,394
[Patent Document 4] Japanese Patent Publication No. 3214975
[Patent Document 5] Japanese Patent Publication No. 3534431
[Patent Document 6] US Patent Application No. 2004/0106817
[Patent Document 7] Japanese Unexamined Patent Application, First Publication No. H10-043595
[Patent Document 8] Japanese Laid-Open Patent Application No. 2001-114740
[Patent Document 9] Japanese Laid-Open Patent Application No. 2001-187771
[Patent Document 10] Japanese Laid-Open Patent Application No. 2003-117397
[Patent Document 11] Japanese Unexamined Patent Application, First Publication No. H8-027089
[Patent Document 12] Japanese Examined Patent Application, Second Publication No. S58-57422
[Patent Document 13] Japanese Unexamined Patent Application, First Publication No. S59-193136
[Patent Document 14] German Patent Application No. 3311521
[Patent Document 15] Japanese Examined Patent Application, Second Publication No. H2-56938
[Patent Document 16] International Publication No. WO 97/33863
[Patent Document 17] Japanese Laid-Open Patent Application No. 2005-162707
[Patent Document 18] Published Japanese translation No. 2003-507180 of PCT International Publication